While the present invention was developed for use in beveling the forward leading edges of aircraft engine cowlings, and is described in this environment, it is to be understood that the invention can be used in other environments where it is necessary to bevel the edge of a compound contoured surface, i.e., a surface that has a contour that varies continually in the degree of arc that it describes.
The contruction and repair of metal or composite aircraft skin requires the smooth joining of sections of sheet metal. This is especially critical around the forward leading edges and aft trim line of the engine cowlings on high-speed aircraft because small protuberances between adjoining skin sections will cause loss of laminar air flow over the cowling and nearby wing surfaces, thus inducing drag and causing loss of lift. Because modern aircraft engine cowlings have compound contoured surfaces, hand-supported portable grinding tools must be used to dress off butt joints around the cowlings. Supporting a heavy grinding tool by hand makes it difficult to bevel a butt joint to achieve a smooth and uniform surface. In addition to being time consuming, the use of hand-supported grinding tools requires skill and experience to accurately perform the operation.
As a result, there is a need for a self-supporting hand-held grinding device that will facilitate precise and efficient beveling of butt joints around a part having a compound contoured surface.
Existing self-supporting portable grinders are unsuitable for a number of reasons. First, such tools typically use a large, flat guide plate for supporting the tool above the part surface in order to achieve a uniform depth of cut. Such a guide plate is unsuitable in the present application because it cannot securely support the tool as it is moved around a compound contoured surface. Another disadvantage is that these tools utilize a guide mechanism that requires reference to a surface other than the edge being bevelled, whereas most aircraft structural surfaces, including engine cowlings, have no such reference surface. A further disadvantage of existing tools is that no means is provided for removing the particles that have been ground off. This is important for the present application because small particles falling into an aircraft engine can damage and possibly destroy the engine. The foregoing and other disadvantages are overcome in the present invention.